So I wanted to perform the AV modification on my Famicom. Google led me to a few different places with quick hacky mods and all of them seemed to have to deal with the jailbars and the infinite number of ways to possibly fix them. I decided to ask the master himself (kevtris) and get the best solution. He said to do it the way Nintendo did it. After searching for the NES schematics and checking them out, I began building my mod. After a few days of working and frustration, I got it working without the jailbar problem. It uses more components but the picture quality is nice. I have traced the NES schematics and included the relevant information in my attachment.

A little explanation about the schematic. First off, this is the first thing I have made with Eagle, I'm just learning it. The inductor is labelled as 'MISC15' and its value is 3.3uh. The three things on the left (H1, H2, and H3) are outputs from the Famicom. 5v, Pin 21 of the PPU, and Ground. The ones on the left (H4 and H5) are the leads going to your TV. All capacitors are ceramic.

In simulation, the gain is entirely immune to a factor of 4 change on the value of R1. This makes sense, because it's a common-collector amplifier (voltage buffer) and the voltage above the transistor should be one diode drop above the voltage out of the PPU.

Let me begin by thanking you guys for your feedback, it is much appreciated.

The schematics I used was the buggy Electronix Corp ones for the NES-001. I do not doubt there are errors, but I have found using this method described works. The 10uf electrolytic capacitor right before the 330ohm resistor causes no video output, so I just omitted it. I do not know how it works. I haven't disassembled my NES (again) to check the schematic. Last night I traced the Twin Famicom's AV circuit, and I will be attempting it next. I have attached it here. D1 is mis-labeled because I cannot identify the diode part number.

So what I have done now was replace the power/RF board from the famicom with a new power supply and I have used the Twin Famicom AV circuit. I pulled my video directly from PPU pin 21. The picture is good. The diode I ended up using was a Panasonic MA2C029W. The characteristics seems to fit, and the diode looks just like the one in the Twin Famicom. More images can be found at http://nesemu2.com/images/fammod/

So I wanted to perform the AV modification on my Famicom. Google led me to a few different places with quick hacky mods and all of them seemed to have to deal with the jailbars and the infinite number of ways to possibly fix them. I decided to ask the master himself (kevtris) and get the best solution. He said to do it the way Nintendo did it. After searching for the NES schematics and checking them out, I began building my mod. After a few days of working and frustration, I got it working without the jailbar problem. It uses more components but the picture quality is nice. I have traced the NES schematics and included the relevant information in my attachment.

A little explanation about the schematic. First off, this is the first thing I have made with Eagle, I'm just learning it. The inductor is labelled as 'MISC15' and its value is 3.3uh. The three things on the left (H1, H2, and H3) are outputs from the Famicom. 5v, Pin 21 of the PPU, and Ground. The ones on the left (H4 and H5) are the leads going to your TV. All capacitors are ceramic.

What are you talking about? Any circuit that doesn't kill chroma in a composite signal isn't going to appreciably blur the luma.Anyway, I tried his circuit in sim; it has no appreciable lowpass effect. The -3dB corner is at 100MHz.

No blurriness. Just some visible dot crawl. It was blurry because of some camera related problems. Here is some new pictures. Don't believe me? Build the circuit and see for yourself! I been running it on a 50-something inch LCD television.

The output looks identical to my twin famicoms video output. Same circuit same results. I decided to use this circuit instead of the "two resistor and a cap" circuits I've seen floating around the internet. This one has been tested and works on millions of televisions world-wide.

Also I would like to take this opportunity to thank the members of #nesdev. Without them I wouldn't be doing anything like this.

What are you talking about? Any circuit that doesn't kill chroma in a composite signal isn't going to appreciably blur the luma.Anyway, I tried his circuit in sim; it has no appreciable lowpass effect. The -3dB corner is at 100MHz.

Oh, good Everything is on the last photo Keep simulating and emulating, i've gotta go. All the best...

I haven't seen 80sFREAK's pictures, but deadbody's mod lokos fine to me. The pictures are a little blurry, but thats just the photos I think. (Granted you'd need better pictures to accurately judge it)

Well I've had this thread bookmarked forever, and finally got around to performing the twin famicom video circuit mod to my original famicom. My primary motivation came from recently upgrading to a commodore 1702 monitor which lacks the RF tuner I made do with on my previous CRT.

Just wanted to share that this circuit worked great for me as well. For others looking to follow along, I also found some new transistors readily available from Digikey that worked well for me. I also used the 1N4148 as l_oliveira suggested.

Analog, video, and BJT's are far from my expertise, but I searched around and found the KSA1015 has comparable specs to the 2SA1015, and it's compliment KSA1815 looked comparable to the 2SC1740.

Also, just to shed some light on required audio modifications to go along with the video. No circuitry is needed, just need to tap from the cartridge audio output directly from the 60pin connector. So that ends up being cartridge pin 46.

Here's some pictures of my install. My goal was minimal intrusion to the console. I favor a modification that can be easily reversed with minimal signs that anything had been touched. Making the console appear that it was designed with AV out was not my goal.. The idea of taking a knife to my famicom makes me cry..

Thinking about picking up some tiny coax to replace my ribbon cables and cheapo RCA connectors, was all I had on had and good enough for now!

Who is online

Users browsing this forum: No registered users and 6 guests

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum